1. Field of the Invention
This invention relates in general to the field of surgical apparatus for removal of cataracts from an eye and in particular to needle apparatus for use with an ophthalmic instrument for removing cataracts.
2. Description of the Prior Art
In general, there are two surgical techniques for removing cataracts from an eye. Surgical removal of cataracts in today's technology may be broadly classified as intracapsular removal and extracapsular removal. With intracapsular removal, the lens and its outer covering, the lens capsule, are both removed. With extracapsular removal, the anterior portion of the lens capsule is opened and then the cataract is removed. The subject matter of the apparatus disclosed and claimed herein applies to the extracapsular method of removal of cataracts.
With the extracapsular method, soft cataracts or the cortex of hard cataracts are removed by aspiration flow through a needle which is inserted in the eye through the sclera. Irrigation flow of an appropriate fluid is simultaneously provided in order to replenish the aqueous fluid aspirated during the surgery and to maintain the normal round shape of the eye during surgery.
Most prior art ophthalmic instruments used in intraocular surgery employ an abrasive technique or a cutting technique to remove the hard portion of cataracts. Hence, the needles associated with these instruments, although using both irrigation and aspiration flow, include means for abrading or cutting the cataracts. Accordingly, such needles do not exactly constitute prior art, but they do give some general insight to the prior problems and their solutions in the general field of intraocular surgery. One such instrument is shown in U.S. Pat. No. 3,994,297, issued Nov. 30, 1976, Ophthalmic Instrument, by J. David Kopf. The needle involved therein comprises an inner tube which reciprocates in an outer tube causing shearing of intraocular tissue which is then aspirated through the inner tube. The outer tube infuses a saline solution back into the eye. Another ultrasonically vibrated needle is disclosed in U.S. Pat. No. 4,041,947, issued Aug. 16, 1977, by Weiss, et al. The inner tube of the needle aspirates the emulsified hard portion of the cataract while an outer tube provides irrigation fluid.
A prior art needle which is relatively well known is illustrated in pending patent application Ser. No. 084,180, filed Oct. 12, 1979, by Daniel M. Eichenbaum, M.D., Disposable Device to be Utilized in Extracapsular Cataract Surgery, and comprises a double-barreled cannular needle. The instrument disclosed therein is for removal of the soft portion of the cataract by the extracapsular technique.
A type of "needle" in another art, but somewhat similar in concept to the apparatus herein, is disclosed in U.S. Pat. No. 4,037,599, issued July 26, 1977, by James D. Raulerson. Said "needle", however, actually comprises a catheter device used in catherization of a blood vessel during hemodialysis and is used to accomplish the delivery of blood to and from a blood vessel as used in hemodialysis treatment.
Notwithstanding the existence of prior art and presently commercial devices, there is still a need for improved irrigation-aspiration flow apparatus to be used with an ophthalmic instrument for extracapsular removal of cataracts.